textproduct: Quad Cities

KEY MESSAGES

- Widespread rainfall is expected this morning through the evening (80-100% rain chances). Accumulations of 1-3 inches are likely (50-70%) along and south of Highway 34, with a Moderate Risk (level 3 of 4) for excessive rainfall remaining across portions of northeast Missouri into west-central Illinois.

- A Marginal Risk (level 1 of 5) for severe weather remains for today, mainly south of Highway 34. The primary threat is damaging winds, with a lower chance of a tornado.

- Weak disturbances and northwesterly flow aloft to keep temperatures comfortable and slightly below average through the end of the week.

SHORT TERM /THROUGH MONDAY NIGHT/

Issued at 150 AM CDT Sun Jun 21 2026

Today...A shortwave trough over the Central Plain ejects eastward into Iowa on Sunday as shortwave ridging pushes against a longwave trough over the eastern CONUS. This enhances the diffluent flow over an accompanying mid-latitude cyclone tracking along the Iowa-Missouri border. A stratiform rain shield is developing north of a warm front extending across northern Missouri in association with a mid-level F-gen band and is forecasted to move into our southeastern CWA as early as 4-5AM. Per the 21.00z HREF run, there will be a sharp gradient in PWATs between the north and south with PWATs near 2 inches south of Highway 34 and 1.4 inches along Highway 20. With the most of the area receiving 9-12 hours of nearly continuous rainfall, accumulations are expected to be high, especially along and south of Highway 34, where a Moderate Risk (Level 3 out of 4) for excessive rainfall and a Flood Watch remains in effective through the evening. Confidence is growing among the CAM ensembles with both the 21.00z runs of the REFS and HREF showing a 50-70% chance of rainfall exceeding 2 inches in this area of interest. North of Highway 34, accumulation amounts will tamper off with the Highway 20 corridor likely (70-90%) only receiving 0.5-1 inch of rainfall.

In terms of severe weather, the SPC's Marginal Risk (Level 1 out of 5) still remains south of Highway 34 where there is the potential for this region to briefly enter the warm sector ahead of the low pressure system, granting more surface based instability. The exact placement of the warm front will dictate the amount of SBCAPE that can encroach northward which is why the probabilities to exceed 250 J/kg is relatively low at 20-40%. That being said, the wind shear will high along the warm front at 40-50 knots in the 0-6-km layer, and the 0-1 km SRH has a medium-to-high chance (50-70%) of exceeding 150 m2/s2. Therefore, any storms that do develop, especially in the afternoon, has the potential to produce damaging winds (5% chance) and a tornado (2% chance).

Highs on Sunday will struggle even to reach 70 degrees north of Highway 34 as the widespread rain and cloud cover should hamper daytime heating. As the low pressure clears the area Sunday evening, the low-level flow shifts to out of the north- northeast, advecting in dry and cool air. Lows will fall back into the 50s Sunday night.

Monday...Subsidence on the backside of the shortwave trough and continued CAA in the low levels clear out of the skies by Monday morning for much of the area as highs climb back into the 70s. By Monday evening, a high pressure will anchor to our north, and winds begin to lighten up. Combining this with the mostly clear skies, Monday night will likely have the coolest lows of the week in the low-to-mid-50s.

LONG TERM /TUESDAY THROUGH SATURDAY/

Issued at 150 AM CDT Sun Jun 21 2026

Tuesday-Wednesday...The next shortwave dives southward into Montana and North Dakota on Tuesday morning. This will deepen a low pressure over the Dakotas, nudging the high pressure to our north eastward and shifting our winds near the surface back to southerly. Enjoy this change a day because this new low pressure swings southeastward into Minnesota and Wisconsin Tuesday night into Wednesday, pushing a cold front southward. The front is forecasted to be the axis of scattered showers and thunderstorms, but luckily, the lack of sufficient return flow from the south and the positive tilt of the trough should limit the severe potential for this storm system. SBCAPE values could struggle to even exceed 750 J/kg along and east of the Mississippi River (10-20% chance). By Wednesday evening, the cold front clears the area with some lingering showers in northwest Illinois on the backside of the low.

Thursday-Saturday...Northwesterly surface flow and subsidence from shortwave trough overhead supports a comfortable Thursday as skies once again clear out with highs in the 70s and low 80s, comfortable for late June. These conditions should persist through Friday afternoon as an elongated high pressure sets up along the Mississippi River Basin. However, similar to Sunday's setup, a weak shortwave in a split flow jet stream ejects into the Central Plain, deepening an elongated Front Range low Friday evening. Looking at the ECMWF and GFS ensembles, there is disagreement on which low pressure center along the lee side of the Rockies will become dominant, but there is agreement on the development of a warm front across the Iowa-Missouri-Illinois region, setting the stage for potentially another day of widespread heavy rainfall.

AVIATION /12Z TAFS THROUGH 12Z MONDAY/

Issued at 623 AM CDT Sun Jun 21 2026

Rounds of showers with embedded storms are expected today, with the main concern being heavy rainfall reducing vis/cigs. Cigs may drop as low as 800-1500 ft as storms move through, with the lower end of that range expected in heavier rainfall at BRL and possibly as far north as MLI. Visibility will generally range between 2-5 SM through the day, although likely lower in any heavy downpours. After 21Z today, we will see shower/storm coverage decrease from west to east, with most becoming dry after 00-03Z Monday. Otherwise, expect increasing east to northeast winds, gusting up to 25 kts through this afternoon/evening as low pressure passes to the south.

DVN WATCHES/WARNINGS/ADVISORIES

IA...Flood Watch through this evening for IAZ087>089-098-099. IL...Flood Watch through this evening for ILZ025-026-034-035. MO...Flood Watch through this evening for MOZ009-010.